The present application relates generally to the field of batteries (e.g., lead-acid starting, lighting, and ignition batteries for vehicles such as automobiles). More particularly, the present application relates to negative grids for use in such batteries and methods for making such negative grids.
Lead-acid batteries typically include a number of cell elements which are provided in separate compartments of a container containing sulfuric acid electrolyte. Each cell element includes at least one positive plate or grid, at least one negative plate or grid, and a porous separator (e.g., a polymeric separator) positioned between each positive and negative plate. The positive and negative plates each comprise a lead or lead alloy grid that supports an electrochemically active material (referred to as a battery paste). The active material is a lead-based material (i.e., PbO, PbO2, Pb or PbSO4 at different charge/discharge stages of the battery) that is pasted onto the grid. The grids provide an electrical contact between the positive and negative active materials which serves to conduct current.
Conventionally, positive and negative grids are manufactured using different processes. For example, positive grids may be made using a number of different methods. One method involves the use of conventional gravity cast book mold operations. Another more recent method involves producing the grids in a continuous process in which a continuous strip of metal (e.g., a lead alloy) that has been previously cast is introduced into a die to remove material therefrom in a punching operation (e.g., using a progressive die) to form the structure of the grids. Individual wires of the grids may be deformed or “coined” to improve battery paste adhesion using a specially-adapted die. Such a process is described in greater detail in the following U.S. patents which are incorporated by reference herein in their entirety: U.S. Pat. Nos. 5,582,936; 5,989,749; 6,203,948; 6,274,274; and 6,953,641.
In contrast, negative grids are typically formed using an expanded metal process. A lead alloy strip is manufactured, either by casting (namely, cast strip) or by casting and rolling (namely, wrought strip), and the strip is subsequently slit and expanded to generate the desired grid pattern in a strip of interconnected battery grids.
It would be desirable to provide an improved method for producing negative grids for use in lead-acid batteries. It would also be desirable to provide negative grids that have features that improve their manufacturability and performance. It would be desirable to provide a grid and/or a method of producing a grid that includes any one or more of these or other advantageous features, as will be apparent to those reviewing the present disclosure.